Computer weigher system with intermediate calculation and display

ABSTRACT

An improved control for an electronic computing scale which computes, for example, the value of an article based upon a predetermined price per unit weight for the article. The weight of the article is multiplied times the predetermined price to obtain the article value which is displayed on a visual readout device. The weight used in computing the value is stored in a memory. The weight of the article is periodically measured and compared with the stored weight. A new value is computed only when a measured weight differs from the weight stored in the memory. The memory is cleared if the predetermined price is changed or the article is removed from the scale. In addition to the value, the predetermined price and the weight stored in the memory are displayed on visual readout devices.

United States Patent .11 1

Loshbough COMPUTER WEIGHER SYSTEM WITH INTERMEDIATE CALCULATION ANDDISPLAY Appl. No.: 310,029

[52] U.S. Cl 177/1, 177/25, l77/DIG. l, 177/DIG. 3, 235/61 PS,235/151.33 [51] Int. Cl G01g 23/22 [58] Field of Search 177/1, 25, DIG.1, 177/DIG. 3; 235/58 PS, 61 PS, 151.33

[56] References Cited UNITED STATES PATENTS 3,608,655 9/1971 Ray et al177/1 3,439,760 4/1969 Allan 235/58 PS X rZ/ WEIGHT 0% /0 g 46 [WEIGHTCOUNTER EMDARATOR DIGITAL SCALE WElGHT REGISTER Nov. 6, 1973 [57]ABSTRACT An improved control for an electronic computing scale whichcomputes, for example, the value of an article based upon apredetermined price per unit weight for the article. The weight of thearticle is multiplied times the predetermined price to obtain thearticle value which is displayed on a visual readout device. The weightused in computing the value is stored in a memory. The weight of thearticle is periodically measured and compared with the stored weight. Anew value is computed only when a measured weight differs from theweight stored in the memory. The memory is cleared if the predeterminedprice is changed or the article is removed from the scale. In additionto the value, the predetermined price and the weight stored in thememory are displayed on visual readout devices.

16 Claims, 2 Drawing Figures VALUE DISPLAY PRICE DISPLAY TlMlNG ANDCONTROL ClRCUlT COMPUTER WEIGHER SYSTEM WITH INTERMEDIATE CALCULATIONAND DISPLAY BACKGROUND OF THE INVENTION weighing articles and computingdesired data from the article weight. Computing scales are, for example,commonly used in the retail food sales industry for weighing meats,produce and similar articles sold by weight and for computing from thearticle weight the value of such article based upon a predeterminedprice per unit weight. The article weight and the computed price arethen displayed to the store clerk and to customers. 1

Computing scales are also used for obtaining data other than the valueof articles. Such scales, for example, are sometimes used for obtaininga count of the number of pieces in a container. The scales weigh thenumber of pieces in the container and divide such weight by the averageweight per piece for obtaining a piece count. Or the scales may be usedfor obtaining a net weight of a material having a known percentage, byweight, of impurities. For example, if. it is known that a particularmaterial has a moisture content of 2 percent by weight, it may bedesired to multiply the reading ofa weighing scale by 98 percent so thatthe net or dry weight of the material is indicated.

Computing scales have become very sophisticated and highly accurate withthe development of digital computing techniques. Advanced computingscales convert the measured article weight into a digital format andmultiply this weight by a price per unit weight or by some other factorin a digital computer. The product appearing at the computer output maythen be displayed on a digital readout, such as a Nixie tube readout ora seven-segment readout. Although state of the art digital computers arefast, they do not, however, have a continuously updated output of thetype available from analog computers which are generally less accurate.Since the output is not continuously updated, the computer mustperiodically multiply the article weight by the price to obtain anaccurate value. Typically, the computed value is updated a few times persecond since it would be expensive to provide an appreciably faster rateand a slower rate is inconvenient for the scale user. However, therelatively slow periodic updating of the computed value results in anobjectionable blinking or blurring of the value and weight shown in thereadout display. One proposed solution to this problem is to use buffermemories before the display. However, this solution is unpracticalbecause of its expense.

SUMMARY OF THE INVENTION According to the present invention, the valuecalculated by a digital computing scale is updated only when there is achange in the article weight or in the price per unit weight to preventunnecessary blinking or blurring of the readout display. The computingscale is provided with a control which periodically cycles to read theweight of an article on a digital weight scale. Each reading of thearticle weight is compared with a weight stored in a memory. If theweights are equal, the cycle is terminated until the next periodicweight reading. If the weights are unequal or do not compare, thecontrol causes the computer to calculate a new value based upon thecurrent weight reading and this weight is stored in the memory forcomparison with future weight readings and for displaying on a digitalweight readout. The newly calculated value and the price from which itwas calculated are also stored and displayed on digital readouts. Thecontrol clears the weight memory to initiate computation of a new valuewhen the price is changed, when the article is removed from the scaleand when the sign of the measured weight changes from negative topositive without a change in the absolute value of the weight.

Accordingly, it is a primary object of this invention to provide animproved control for computing scales.

Another object of this invention is to provide an improved method andapparatus for reducing blinking and blurring of a digital readout in acomputing scale.

Other objects and advantages of the invention will become apparent fromthe following detailed description, with reference being made to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagramillustrating an improved electronic computing scale incorporating acontrol constructed in accordance with the present invention; and

FIG. 2, consisting of FIGS. 2a, 2b and 2c, is a detailed logic diagramof a control and computer for an electronic digital computing scaleconstructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRE EMBODIMENTS v Turning now to FIG. 1, a blockdiagram is shown for an improved electronic computing scale 10 embodyingthe principles of the present invention. The scale 10 is shown anddescribed for computing and indicating the value of an article beingweighed based upon a predetermined price per unit weight. However, itwill be appreciated that by using a factor other than price, data otherthan value will be computed and indicated by the scale 10. It, forexample, the reciprocal of the average weight of one of several piecesbeing weighed is multiplied times the total piece weight, the scale 10will indicate a count of the total number of pieces being weighed. Or,the scale 10 may be used for obtaining a net weight of a material havinga predetermined moisture content or other impurity by entering the netweight percentage into the scale computer in place of price.

Weight data is obtained by a conventional digital scale 11. The digitalscale 11 may, for example, consist of a scale on which a shaft isrotated in proportion to the weight of an article placed on a platform.A Gray code chart may be rotated by the shaft. Optical sensors read theGray code chart and this reading is converted to a binary coded decimal(BCD) output which is supplied to a weight register 12 in the computingscale 10. Or the digital scale 11 may consist of a load cell scale whichgenerates an analog signal proportional to the weight placed upon one ormore load cells. The analog signal is then applied to ananalog-to-digital converter 3 forgenerating a BCD digital weight outputwhich is applied to the weight storage register 12.

The digital scale 11 is provided with two inputs from a timing andcontrol circuit 13. When a weight reading is to be entered into theweight register 12, the timing and control circuit 13 enables the outputof the digital scale 11 and then applies four clock pulses for seriallyshifting four BCDs into the weight register 12. In the followingdescription, the four BCDs shifted into the weight register 12 willrepresent ten pounds, one pound, one-tenth pound and one-hundredth poundHowever, it will be appreciated that other units of weight or additionalunits of weight also may be used. The digitalscale 11 is provided withseveral outputs in addition to the weight outputs: an output is providedfor indicating when the capacity of the digital scale 11 has beenexceeded, an output is provided for indicating when the scale weightoutput is below zero or has a negative sign as when the scale 11 iscompensated for a tare weight and no container or package is placed onthe scale 11 and an output is provided for generating a pulse when theweight on the scale 11 drops below one-tenth pound on removal of anarticle being weighed. Since digital scales having inputs and outputs ofthis type are known and obvious to those skilled in the art, the digitalscale 11 will not be discussed in further detaiL.

A clock 14 periodically causes the timing and control circuit 13 tocycle to enable the digital scale and read into the weight register 12four BCD weight digits corresponding to the weight of an article beingweighed. Each time a new weight is entered into the register 12, acomparator 15 compares this weight with a weight stored in a memory orweight counter 16. If the weights in the register 12 and the weightcounter 16 compare, the timing and control circuit 13 inhibits thecalculation of a new value for the remainder of a control cycle. If, onthe other hand, the two weights do not compare, the timing and controlcircuit 13 supplies a series of pulses to a computer 17.

A manual keyboard 18 is provided for entering into the computing scale10 the price per pound of the article being weighed. The keyboard 18 maybeof a conventional type, such as a IO-key keyboard of the type foundonelectronic adding machines. The keyboard 18 includes a decimal-to-BCDencoder such that the price data appears in a BCD format which isentered intoa price register 19. For retail food sales, it may beassumed that the normal maximum price per pound is no more than $9.99.Therefore, the price register 19 normally will be adequate if hiscapable of storing three BCDs corresponding to three digits of price.The price per pound stored in the register 19 is applied to the computer17. The computer 17 generates an output corresponding to the product ofthe weight stored in the weight register 12 and the price per poundstored 'in the price register 19. This product is equal to the value ofthe article being weighed and is stored in a value register 20. At thesame time the computer 17 is calculating a value for storage in thevalue register 20, the weight counter 16 is counted up to the weightstored in the weight register 12.

The electronic computing scale 10 is provided with three digitaldisplays for visually indicating weight, price and value. A display 21is connected to the weight counter 16 for indicating the weight storedin the weight counter 16. Similarly, a display 22 indicates the value ofthe article being weighed, as stored in the value register 20, and adisplay 23 indicates the price per pound of the article, as stored inthe price register 19. During a cycle of the timing and control circuit13 in which the contents of the weight register 12 and the weightcounter 16 do not compare, the timing and control circuit 13 clears theweight counter 16 and the value register 20. These registers are alsocleared in the event that a new price is entered into the price register19 from the keyboard 18, or the keyboard 18 isv cleared, or the outputof the digital scale 11 drops below a predetermined low value, such asone-tenth pound, when the article being weighed is removed from thescale 11.

Referring now to FIG. 2, which consists of FIGS. 2a, 2b and 20, detailedlogic is shown for the electronic computing scale 10. To facilitatereading FIG. 2, the output of any element extending between two sheetsof FIG. 2 is designated with the number of the element primed. Forexample, the output of gate 67 is designated 67' where it extendsbetween FIGS. 2b and 2c.

A control counter 30 controls the overall cyclic operation of theelectronic computing scale 10 in response to a clock 31 and a clock 32.The clock 31 generates relatively low frequency pulses for periodicallyrecycling the control counter 30. It has been found, for example, that a5 Hz. clock rate is satisfactory for updating the displayed articlevalue up to five times per second. Each one-fifth second, the clock 31clears a flipflop 33. When cleared, the Q output of the flip-flop 33disables and, at the same time, clears the control counter 30 forinitiating a new cycle. The clock 32 has a relatively high frequencypulse output, for example, on the order of l mI-lz., which is appliedthrough a divide-by-sixteen circuit 34 consisting of a 4-bit counter toset the flip-flop 33 shortly after it is cleared by the clock 31.

When the flip-flop 33 is set, the control counter 30 is again enabledfor cycling. The intermediate frequency clock output of the counter 34is applied on a scale clock output terminal 35 to clock data from thedigital scale 11. At the same time, the clock output of the counter 34is applied through an inverter 29 to count up the control counter 30.During the counts of zero through three at the outputs of the controlcounter 30, an AND gate 36 will also apply a signal on an enable output37 for reading the output of the digital scale 11. When scale 11 isenabled by a signal on the enable output 37, four clock pulses appearingon the scale clock output 35 clock the four BCD weight digits into theweight register 12 on four weight data lines 38.

' At the same time, a NAND gate 39 having inputs connected to the scaleclock output 35 and the enable output 37 shifts the weight data into theweight register 12.

The weight register 12 consists of four 4-bit shift registers 40-43. Theones bit for each of the four BCDs is stored in the register 40, thetwos bit for each of the BCDs is stored in the register 41, the foursbit for each of the BCDs is stored in the register 42 and the eights bitfor each of the BCDs is stored in the register 43. The outputs of theregisters 40-43 are applied to compare circuits 44-47 for comparisonwith the corresponding bits of the BCDs stored in the weight counter 16.The weight counter 16 consists of four 4-bit decoder counters 48-51. Theoutputs of the counters, as previously stated, are applied to thecomparator circuits 44-47, respectively. The comparators 44-47 have acommon output 52 which goes to a high or logic one state uponcoincidence of the contents of the registers 40-43 and the counters48-51.

As indicated above, the weight output from the digital scale 11 is readinto the shift registers 40-43 during the counts of zero through threeof the control counter 30. On a count of four, and succeeding counts,the AND gate 36 will apply a signal on the output 37 for inhibiting anoutput from the digital scale 11 and for inhibiting the gate 39 fromshifting the registers 40-43. The change in output of the AND gate 36also triggers a coincidence flip-flop 53. The output 52 from thecomparator is connected through an inverter 54 to the clear and the Jinputs of the flip-flop 53. 1f the weight stored in the weight register12 compares identically to the weight stored in the weight counters 16,the flip-flop 53 will remain in a cleared state with a high 6 output.However, if there is no coincidence, the flipflop 53 will be set and the6 output of the flip-flop 53 will change the output of a NAND gate 55which is in turn applied to a NAND gate 56. On a'count of five, theoutput of the gate 56 will be changed. This output is applied through anOR gate 57 and an inverter 58 for forming a main reset signal whichclears the 4-bit counters 48-51 of the weight counter 16 and clears andpresets for roundoff a portion of the value counter 20. The main resetsignal is also applied through an OR gate 59 for clearing the remainingportion of the value counters 20, as will be discussedin detail below.

As the control cycle continues, the control counter 30 is counted up toa total count of six. On a count of six, a NAND gate 65 will disablefurther counting by the control counter 30. The control counter 30 willalso apply a signal to an AND gate 66 which enables the computer 17. lfthere has been weight coincidence, the AND gate 66 will have no outputand the cycle is terminated until the control counter 30 is cleared bythe clock 31 to initiate a new cycle. If the flip-flop 53 was set oncount four in response to a lack of coincidence, the AND gate 66 willhave an output which enables a NAND gate 67. The output of the clock 32is connected through an inverter 68 to the gate 67. Clock pulses passthrough the enabled gate 67 to the computer 17, as will be discussed indetail below. The clock output of the inverter 68 is also-appliedthrough a NAND gate 69 to the computer 17. The NAND gate 69 is enabledby the output of the OR gate 57 when the flip-flop 53 is set.Simultaneous clock outputs are required from both gates 67 and 69 foroperating the computer 17.

The clock outputs of the NAND gates 69 and'67 are connected through anAND gate 70 to count up a counter and sixteen-line decoder 71 in thecomputer 17. The counter and decoder 71 may comprise an integratedcircuit such as a type 74161 TTL counter connected to a type 74155 TTLdecoder/demultiplexer or it may consist of any other suitable elementhaving outputs on counts of nine, ten, twelve and fifteen out of everycycle. The nine, ten, twelve, fifteen and carry outputs of the counterand decoder 71 are used for controlling multiplication by the computer17. The counter and decoder 71 is cycled by the clock output of the ANDgate 70 once for each unit of the weight stored in the weight register12. The carry output of the counter and decoder 71 is connected tocountup the weight counter by one on each cycle of 16 pulses from the clock32. When the weight counter 16 is the NOR gate 80 to the multiplierscounted up to coincidence with the weight register 12, the coincidenceflip-flop 53 is cleared thereby inhibiting the passage of clock pulsesthrough the NAND gates 67 and 69 and the AND gate to the counter anddecoder 71.

.The price data is supplied to the computer 17 from the price register19. The price register 19 is shown as consisting of four 4-bit shiftregisters 72-75. BCD price data is serially shifted from the keyboardand decoder 18 into the shift registers 72-75 over four data lines 76.Since there are only three price digits in the embodiment of thecomputing scale 10 described herein, only three outputs of the shiftregisters 72-75 are used. The

three outputs of the register 72 are the ones bit for each of the threedigits, the three outputs of the register 73 are the twos bit, the threeoutputs of the register 74 are fours bit and the three outputs of theregister 75 are the eights bit.

The three price BCDs are applied, respectively, to three decadedecimalrate multipliers 77-79, with the $.01 digit applied to the multiplier77, the $.10 digit applied to themultiplier 78and the $1.00 digitapplied to the multiplier 79. The decade-decimal rate multipliers arecommercially available units such as Texas Instrument type 74167 TTLintegrated circuits. The output of each multiplier 77-79 is equal toone-tenth the input number from the price registers 72-75 times thepulse input applied to the multipliers 77-79 from a NOR gate 80. The NORgate 80 receives clock pulses over the line 67' from the NAND gate 67during the multiplication cycle. Since no pulse is required for a zero,nine clock pulses are passed through the NOR gate 80 during each cycleof the counter and decoder 71.

When the counter and decoder 71 reaches a count of nine, the nine outputis applied through an inverter 81 to set a flip-flop 82 when triggeredby the next clock pulse on the line 67'. When the flip-flop 82 is set,an OR gate 83 inhibits the passage of clock pulses through 77-79 andalso disables the input to the multipliers 77-79. Further counting ofthe multipliers 77-79 is inhibited until the counter and decoder 71completes a cycle. At the completion of a cycle of the counter anddecoder 71 at a count of fifteen, a NOR gate 84 clears the flip-flop 82to reinstate the input to the multipliers 77-79. An inverter 85 alsoconnects the output of the NOR gate 84 to the OR gate 83 for preventingthe multipliers 77-79 from being counted up simultaneously as theflip-flop 82 is cleared on a fifteen count. Thus, it will be apparentthat the clock pulse input to the multipliers 77-79 is ten times theclock pulse input to the weight counters 16. This is to compensate forthe fact that the commercial multipliers 77-79 used in the computer 17divide the output by a factor of 10.

The value counter 20 consists of six 4-bit decoder counters 89-94. Thecontents of the counter 89 is equivalent to $0001; the contents of thecounter 90 is equivalent to $.00l; the contents of the counter 91 isequivalent to $.01; the contents of the counter 92 is equivalent to$.10; the contents of the counter 93 is equivalent to $1.00; and thecontents of the counter 94 is equivalent to $10.00. The value counter 89is initially cleared by the main reset output line 58' from the inverter58 and the counters 91-94 are cleared by the output 59' of the OR gate59. The main reset line 58' is also connected to the load or preset"terminal of the counter 90. The binary input to the counter 90 is wiredfor presetting the counter 90 to five or in monetary value to $.005 forrounding off the value of the nearest cent. In addition to a signal onthe load terminal, the counter 90* must be clocked through at least onecycle.

The output of the decimal-decade rate multiplier 77 is applied to countup the counter 89. The counter 89, and the other counters 90-94, are ofthe decade type and have, in addition to a binary BCD output, a carryoutput on a count of ten. The carry output of the counter 89 sets aflip-flop 95 which was previously cleared by the output of the NOR gate84, at the same time the flip-flop 82 was cleared. When the counter 89is counted up by more than ten and the carry output sets the flip-flop95, a pulse passes through an AND gate 96 to a carry input to themultiplier 78 on the ten count of the counter and decoder 71. The carryinput of the multiplier 78 is applied to the multiplier output throughan internal OR circuit. The output of the multiplier 78 passes throughan OR gate 97 to clock the counter 90 of the value register 20. Thecontrolled clock output 69' of the gate 69 is also applied through aninverter 88 to the OR gate 97 to preset the counter 90 when the counters89 and 91- 94 are cleared. When the counter 90 has cycled, the carryoutput is used to set a flip-flop 98. The output of the flip-flop 98 isapplied through an .AND gate 99 to the carry" input of thedecade-decimal rate multiplier 79 on a count of twelve by the counterand decoder 71. The output of the multiplier 79 counts upv the remainingcounters 91-94 of the value counter 20. As previously indicated, thecounting operation continues until weight coincidence clears theflip-flop 53. At this time, clock pulses to the counter and decoder 71cease and the value stored in the counters 91-94 corresponds to thevalue to the nearest cent of the article on the digital scalell. Formost retail food sales, the value will not exceed $99.99. If this valueshould be exceeded, the carry output 94' of the most significant digitcounter 94 will set a flip-flop 100. The 6 output of the flip-flop 100is applied through the OR gate 59 to clear the value counters 91-94 inresponse to setting the flip-flop 100, thereby preventing the display ofan erroneous value.

The computing scale includes a display panel for displaying weight,value and price information to an operator. The weight of an article onthe digital scale 11 is displayed on the weight display 21 whichconsists of four decoder-driver and display units 101-104. The displayunit 101 has an input from the weight counter 48 and indicates 0.0lpound units; the display unit 102 has an input from the weight counter49 and indicates 0.1 pound units; the display unit 103 has an input fromthe weight counter 50 and indicates one pound units; and the displayunit 104 has an input from the weight counter 51 and indicates ten poundunits. The value display 22 also consists of four decoder-driver anddisplay units 105-108 with the display unit 105 having an input from thevalue counter 91 for indicating value in $.01 units, the display unit106 having an input from the counter 92 for indicating value in $.10units, the display unit 107 having an input from the counter 93 forindicating value in $1 units and the display unit 108 having an inputfrom the counter 94 for indicating value in $10 units. Finally, theprice stored in the price register 19 is displayed on the price display23 which consists of a decoder-driver and display unit 109 forindicating price in $.01 units, a decoder-driver and display unit 110for indicating price in $.10 units and a decoder-driver and display unit111 for indicating price in $1 units.

It will be appreciated that the decoder-driver and display units 101-111may be of any conventional design. They may, for example, consist of anintegrated circuit BCD-to-seven segment decoder-driver and a sevensegment display device. Or, the units 101-111 consist of aBCD-to-decimal decoder-driver and a ten 'digit display such as a Nixietube.

It is of a primary concern that erroneous weight and value data cannotbe displayed on the weight display 21 or the value display 22,respectively. A number of interlocks are provided for preventingerroneous displays. As previously indicated, the value counters 91-94are cleared by the flip-flop 100 and the OR gate 59 if the capacity ofthese counters is exceeded. Thus, if an article has a value over $99.99,such as $124.34, the counters 91-94 will be cleared rather than storingand causing an indication of an erroneous value of $25.34. 1

It is also desirable to prevent an erroneous'price indication in theevent that either the price register 19 is cleared or new price data isentered into the price register 19 without a change in the articleweight and also when an article being weighed is removed from thedigital scale 11. If a clear button is pushed on the keyboard 18, aclear output 115 applies a signal through an OR gate 116 to a left-rightshift mode input to the price shift registers 72-75 to cause the nextfour clock pulses on the clock line 68 to empty the shift registers72-75. The output of the OR gate 116 is also applied through an inverter117 and an OR gate 118 to the OR gate 57. This causes the OR gate' 57and the inverter 58 to generate a main reset signal on the main resetline 58, thereby clearing the weight counters 16 and the value counters89 and 91-94 and presetting the value counter 90 to five for round offof the next computed value. These counters are also cleared or preset ina similar manner when new data is entered into the price shift registers72-75. Each time a BCD is entered into the registers 72-75, the keyboard18 generates an enter data output 119 which triggers a Schmitt trigger120. When the Schmitt trigger 120 is triggered, a pulse passes through acapacitor 121, the OR gate 118, the OR gate 57 and the inverter 58 forapplying a signal on the main reset line 58'. The output 120 of theSchmitt trigger 120 is also applied to the right shift input of theprice registers 72-75 for shifting a price digit in a BCD format fromthe keyboard and decoder 18 into the price registers 72-75.

As previously mentioned, the digital scale 11 which weighs the articlebeing priced is designed to generate a pulse each time the output of thescale 11 drops through a predetermined low limit, such as one-tenthpound, as a consequence of the article being removed from the digitalscale 11. This pulse is applied by the digital scale 11 on a line 122 tothe OR gate 116 for automatically clearing the price register 19, theweight register 16 and the value register 20 in the same manner in whichthese registers are cleared by a clear output 115 from the keyboard 18.Thus, price data may be entered into the computing scale 10 through thekeyboard 18 either before or after an article is placed upon the digitalscale 11. When the article is placed upon the digital scale 11 and theprice is entered, a value is computed and displayed. After the value is9 computed and displayed, the weight, price and value registers arecleared upon removal of the article from the digital scale 11. Thisinterlock prevents an erroneous value indication if a careless operatorforgets to enter a new price when weighing articles having differentprices per pound.

It is also desirable to have an interlock to prevent er- 'roneous valueand weight displays when the maximum weight capacity of the digitalscale 11 is exceeded. A flip-flop 123 is provided as a memory forstoring information on whether or not the capacity of the digital scale11 is exceeded. On a count of three from the control counter 30, a NANDgate 124 clears the flip-flop 123. The digital scale 11 is provided withan overcapacity output 125 connected to the J input of the flip-flop123. If the capacity of the scale is exceeded,

the flip-flop 123 will be set by the NAND gate 65 on a count of six fromthe control counter 30. When the flip-flop 123 is set, a NOR gate 126changes the output of the OR gate 59'for clearing the value counters91-94, thereby preventing an erroneous value indication. Setting of theflip-flop 123 also applies a signal through an inverter 127 to blank theweight decoderdriver and display units 101-104. Thus, with all weightdigits blanked, a user of the computing scale 10 will realize that theweight capacity of the scale 10 has been exceeded. I

A final interlock is provided for indicating on the weight display 21 anegative sign when the weighton ,the digital scale 11 is below zero andalso for inhibiting a value display when the weight is below zero. Manycommercial digital scales 11 of the type suitable for use with theherein described computing scale 10 include a tare provision. Thedigital scale 11 may be initially set to read below zero by an amountequal to the tare weight of a package or container which holds thearticle being priced. If no articles are placed on the digital scale11,- it may be desirable to indicate the negative value of thetareweight, even though it would not be desirable to calculate a value basedupon this negative weight.

A flip-flop 128 is provided for controlling the sign of the weightstored in the weight counters 48-51. The flip-flop 128 is initiallycleared on a count of three of the control counter 30by the NAND gate124 at the same time'the flip-flop 123 is cleared. The digital scale 11is provided with a sign output 129 which changes logic states'when goingbetween below zero and above zero weight'readings. The sign output- 129of the scale 11 is applied through an inverter 130 to the J input of theflip-flop 128. On a count of six by the control counter 30, the NANDgate 65 triggers and sets the v causing this display to indicate'theminussign. At the same time, the flip-flop 128 applies a signal to theNOR gate 126 to clear the value counters 91-94, thereby preventing ameaningless value display.

Since the timing and control circuit '13 looks for a comparison betweenthe weights stored in the weight register 12 and the weight counter 16,provision must be made for initiating a new value computation in theevent that the scale goes from a negative weight to a positive weight ofthe same magnitude. Thus, if the digital scale 11 is preset to anegative value for a one-half pound tare weight and an article in acontainer having a total weight of one pound is placed upon the digitalscale 11, the weight register 12 will continue to read one-half poundresulting in coincidence even though the signal has gone from a negativevalue to a positive value. Therefore, the below zero output 129 of thescale 11 and the Q output of the sign flip-flop 128 are connectedthrough a NAND gate 132 to the NAND gate 55. A change in sign in theoutput of the digital value will then'be computed on the next cycle ofthe control counter 30.

It will be appreciated by those skilled in the art that various changesand modifications may be made to the above-described electroniccomputing scale 10 without departing from the invention. It will, ofcourse, be appreciated that the computer 17 may be of various commercialdesigns and may, for example, use a partial product method ofmultiplication. In addition, the computer 17 may provide othermathematical computations, such as division, for computing other databased upon an article weight and a weight related factor other thanprice per pound. If, for example,.a weight factor which .is equal to theaverage piece weight of several pieceson the digital scale 11 is enteredinto the register 19 and the computer 17 is adapted to divide the weighton the digital scale 11 by the piece weight in the register 19, then thedisplay 22 will indicate a count of the number of pieces on the digitalscale 11. Furthermore, it will be appreciated that the design of thedigital scale 11 and the keyboard 18 may be varied, as well as theformat in which data is supplied from the digital scale 11 and thekeyboard 18 Various other changes and modifications may also be madewithout departing from the spirit and the scope of the claimedinvention.

What I claim is:

1. An improved computing scale which displays desired data calculatedfrom a predetermined weight factor for an article and a measured weightof such article comprising, in combination, means for periodicallymeasuring the weight of the article, computing means for calculating thedesired data from such measured weight and the weight factor, memorymeans for storing such calculated data until new data is calculated,means for displaying the data stored in said data memory' means, andmeans for inhibiting said computing means from calculating new data whena measured weight is the same as the immediately preceding measuredweight.

2. An improved computing scale, as set forth in claim 1, wherein saidinhibiting means includes memory means for storing the measured weightfrom which the stored data was calculated, means for comparing eachperiodic measured weight with such weight stored in said weight memorymeans, means for causing said computing means to calculate new data fromany periodic measured weight which differs from such stored weight, andmeans for storing in said weight memory means any periodic measuredweight which differs from such stored weight.

3. An improved computing scale, as set forth in claim 2, and includingmeans for displaying the article weight stored in said weight memorymeans.

4. An improved computing scale, as set forth in claim 3, wherein saidweight measuring means has a maximum weight capacity, and includingmeans for blanking at least a portion of said weight displaying meanswhen such maximum weight capacity has been exceeded.

5. An improved computing scale, as set forth in claim 2, wherein saidweight measuring means has a maximum weight capacity, and includingmeans for clearing said data memory means when such maximum weightcapacity has been exceeded.

6. An improved computing scale, as set forth in claim 2, and includingmeans for clearing said weight memory means when the article is removedfrom said weight measuring means.

7. An improved computing scale, as set forth in claim 2, and includingmeans for clearing said weight memory means in response to a change insuccessive weight measurement from a negative value to a positive value.

8. An improved computing scale, as set forth in claim 2, and includingmemory means for storing the predetermined weight factor, means forchanging the stored weight factor, and means responsive to a change inthe stored weight factor for clearing both said weight memory means andsaid data memory means.

9. An improved computing scale, as set forth in claim 2, wherein saiddata memory means has a maximum memory capacity, and including means forclearing said data memory means in response to calculated data exceedingsuch maximum memory capacity.

10. A-method for calculating and displaying the value of an articlehaving a predetermined price per unit weight comprising the steps of:periodically measuring the weight of the article; comparing eachsuccessive measured weight with a weight stored in a weight memory; inthe event that any measured weight differs from the stored weight,calculating a new value from such measured weight and the predeterminedprice per unit weight; displaying the most recent calculated value; andstoring in said weight memory the measured weight from which suchdisplayed value was calculated.

1 l. A method for calculating and displaying the value of an articlehaving a predetermined price per unit weight, as set forth in claim 10,and including the step of clearing said weight memory when the articleexceeds a predetermined maximum weight.

12. A method for calculating data based upon the weight of an articleand a weight factor, comprising the steps of: storing the weight factorin a memory; periodically measuring the weight of the article; comparingeach successive measured weight with a weight stored in a weight memory;in the event that any measured weight differs from the stored weight,calculating new data from such measured weight and the stored weightfactor; storing the most recent calculated data in a memory; displayingthe stored data; and storing insaid weight memory the measured weightfrom which such displayed data was calculated.

13. A method for calculating data based upon the weight of an articleand a weight factor, as set forth in claim 12, and including the step ofclearing said weight memory each time a new weight factor is stored insaid weight factor memory.

14;. A method for calculating data based upon the weight of an articleand a weight factor, as set forth in claim 12, and including the step ofclearing said weight and data memories whenever a measured weightexceeds a predetermined maximum weight.

15. A method for calculating data based upon the weight of an articleand a weight factor, as set forth in claim 12, and including the step ofclearing said data memory whenever the calculated data exceeds apredetermined maximum limit.

16. A method for calculating data based upon the weight of an articleand a weight factor, as set forth in claim 12, and including the step ofclearing said weight, weight factor and data memories wheneversuccessive measured weights drop below a predetermined low level.

1. An improved computing scale which displays desired data calculatedfrom a predetermined weight factor for an article and a measured weightof such article comprising, in combination, means for periodicallymeasuring the weight of the article, computing means for calculating thedesired data from such measured weight and the weight factor, memorymeans for storing such calculated daTa until new data is calculated,means for displaying the data stored in said data memory means, andmeans for inhibiting said computing means from calculating new data whena measured weight is the same as the immediately preceding measuredweight.
 2. An improved computing scale, as set forth in claim 1, whereinsaid inhibiting means includes memory means for storing the measuredweight from which the stored data was calculated, means for comparingeach periodic measured weight with such weight stored in said weightmemory means, means for causing said computing means to calculate newdata from any periodic measured weight which differs from such storedweight, and means for storing in said weight memory means any periodicmeasured weight which differs from such stored weight.
 3. An improvedcomputing scale, as set forth in claim 2, and including means fordisplaying the article weight stored in said weight memory means.
 4. Animproved computing scale, as set forth in claim 3, wherein said weightmeasuring means has a maximum weight capacity, and including means forblanking at least a portion of said weight displaying means when suchmaximum weight capacity has been exceeded.
 5. An improved computingscale, as set forth in claim 2, wherein said weight measuring means hasa maximum weight capacity, and including means for clearing said datamemory means when such maximum weight capacity has been exceeded.
 6. Animproved computing scale, as set forth in claim 2, and including meansfor clearing said weight memory means when the article is removed fromsaid weight measuring means.
 7. An improved computing scale, as setforth in claim 2, and including means for clearing said weight memorymeans in response to a change in successive weight measurement from anegative value to a positive value.
 8. An improved computing scale, asset forth in claim 2, and including memory means for storing thepredetermined weight factor, means for changing the stored weightfactor, and means responsive to a change in the stored weight factor forclearing both said weight memory means and said data memory means.
 9. Animproved computing scale, as set forth in claim 2, wherein said datamemory means has a maximum memory capacity, and including means forclearing said data memory means in response to calculated data exceedingsuch maximum memory capacity.
 10. A method for calculating anddisplaying the value of an article having a predetermined price per unitweight comprising the steps of: periodically measuring the weight of thearticle; comparing each successive measured weight with a weight storedin a weight memory; in the event that any measured weight differs fromthe stored weight, calculating a new value from such measured weight andthe predetermined price per unit weight; displaying the most recentcalculated value; and storing in said weight memory the measured weightfrom which such displayed value was calculated.
 11. A method forcalculating and displaying the value of an article having apredetermined price per unit weight, as set forth in claim 10, andincluding the step of clearing said weight memory when the articleexceeds a predetermined maximum weight.
 12. A method for calculatingdata based upon the weight of an article and a weight factor, comprisingthe steps of: storing the weight factor in a memory; periodicallymeasuring the weight of the article; comparing each successive measuredweight with a weight stored in a weight memory; in the event that anymeasured weight differs from the stored weight, calculating new datafrom such measured weight and the stored weight factor; storing the mostrecent calculated data in a memory; displaying the stored data; andstoring in said weight memory the measured weight from which suchdisplayed data was calculated.
 13. A method for calculating data basedupon the weight of an article and a weight factor, as set forth in claim12, and including the step of clearing said weight memory each time anew wEight factor is stored in said weight factor memory.
 14. A methodfor calculating data based upon the weight of an article and a weightfactor, as set forth in claim 12, and including the step of clearingsaid weight and data memories whenever a measured weight exceeds apredetermined maximum weight.
 15. A method for calculating data basedupon the weight of an article and a weight factor, as set forth in claim12, and including the step of clearing said data memory whenever thecalculated data exceeds a predetermined maximum limit.
 16. A method forcalculating data based upon the weight of an article and a weightfactor, as set forth in claim 12, and including the step of clearingsaid weight, weight factor and data memories whenever successivemeasured weights drop below a predetermined low level.